This invention is in the field of plant breeding. In particular, this invention relates to the development of heat tolerant broccoli (Brassica oleracea L. var. italica).
Broccoli (Brassica oleracea L. var. italica) has become an increasingly popular crop worldwide especially in health-conscious areas of the western world such as the North America, Europe, and Japan. An average broccoli stalk contains only 30 calories and provides 240% of the recommended daily allowance of vitamin C plus 10% of the recommended daily allowance of vitamin A. In addition to its nutritional value, some recent studies have shown that broccoli aids in the prevention of some forms of cancer.
Broccoli is a cool weather crop. High temperatures ( greater than 80xc2x0 F.) for even relatively short periods of time and warm temperatures ( greater than 75xc2x0 F.) for extended periods of time cause broccoli heads to be rough with uneven flower bud sizes and thus commercially unacceptable. {(Bjxc3x6rkman, T., et al. (1998) High temperature arrest of inflorescence development in broccoli (Brassica oleracea var. italica L.) Journal of Experimental Botany 49:101-106.} As a result of the high sensitivity to heat during growth, broccoli can only be grown in limited areas under cool weather conditions.
Previous attempts at identifying heat tolerant broccoli cultivars have not been successful because broccoli is sensitive to relatively short periods of heat stress thereby making field observations too variable for effective genetic screening. Bjxc3x6rkman, et al. (1998).
Thus, there is a need to develop heat tolerant broccoli varieties that will produce commercially acceptable broccoli heads under warm weather heat stress growth conditions. In addition, there is a need to develop heat tolerant broccoli inbred lines useful for producing heat tolerant F1 seed.
In order to meet these needs, the present invention is directed to heat tolerant broccoli plants. In particular, this invention is directed to broccoli seed capable of germinating and growing into a plant capable of producing a commercially acceptable head under heat stress growth conditions.
The broccoli seed of this invention are capable of germinating into a plant capable of producing a commercially acceptable head under heat stress growth conditions that render the heads of commercially available broccoli commercially unacceptable.
In addition to being heat tolerant, the broccoli seed of this invention are capable of germinating into a plant that is predominately mildew resistant.
The broccoli seed of this invention will produce a plant with a commercially acceptable head when the plant is exposed to a maximum temperature of 90xc2x0 F. for at least 5 consecutive days during the growth cycle; when the plants are exposed to a maximum temperature of at least 95xc2x0 F. for at least one day during the growth cycle; when the plants are exposed to a maximum temperature of 85xc2x0 F. for at least 15 days during the growth cycle; when the plants are exposed to a maximum temperature of at least 75xc2x0 for at least 25 days during the growth cycle; when the plants are exposed to a maximum temperature of at least 80xc2x0 C. for at least 20 days during the growth cycle and other heat stress growth conditions.
The broccoli seed of this invention include but are not limited to those seeds designated M7028, M7007, M7009, M7022, 393-2-19, H7008, H7022, 393-2-47, 98-2192, 98-2088, 98-2061, H7007, H7028, H7010, and H7021R. The broccoli seed of this invention further include lines 4243, 4221, 4441, 4274-1, 4274-2, 4278-1, 4284-1, 4285-1, 4354-1, 4354-2, 4377-1, 4318-1, 4320-1, 4320-2, 4321-1, 4437-1, 4476-1, 4462-1, 4308-2, 4309-1, 4355-1, 4412-1, 4301, 4303, 4304, 4317, 4468, 4470, 4471, 4263-1, 4430-1, 4450-1, 4450-2, 4432-1, 4267-1, 7861, 7864, 7865, 7881, 7887, 7935, 8092, 7883, 7914, 7770, 7778.
The broccoli seed of this invention further include lines 4201, 4219, 4237, 4280, 4287, 4288, 4289, 4290, 4291, 4458-1, 4460-1, 4415, 4418, 4395-2.
Each of the lines of this invention can be crossed with other broccoli lines.
The broccoli seeds of this invention include inbred lines, hybrid lines, male lines and female lines, all of which are heat tolerant and capable of producing a commercially acceptable head under heat stress growth conditions.
This invention is further directed to broccoli plants or parts of broccoli plants produced from the broccoli seed of the invention. The invention is further directed to broccoli plants regenerated from tissue culture of the broccoli plants of this invention. The tissue culture of the invention comprises regenerable cells including meristematic tissue, anthers, leaves, ovules, roots, embryos, protoplasts and pollen and plants regenerated from these cells.
The invention is further directed toward transgenic heat tolerant broccoli plants. The transgenic heat tolerant broccoli lines may be resistant to various herbicides or pesticides.
The invention is further directed to broccoli plants having all of the phenotypic characteristics of the plants produced from the heat tolerant broccoli seed of the invention. The invention is further directed to plants resulting from selecting, crossing, breeding or otherwise altering the broccoli plants of this invention.
The invention is further directed to biological material isolated from the plants of this invention. Such material includes but is not limited to RNA, DNA, protein and carbohydrate. The DNA of these plants includes the gene(s) involved in heat tolerance.
This invention is further directed to the seeds and plants produced from crossing other broccoli lines with plants grown from the seed of this invention.
This invention is further directed to methods of breeding heat tolerant broccoli lines.